CVE-2026-63994 (GCVE-0-2026-63994)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-08-05 12:37
VLAI
Title
tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()
Summary
In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head. Fix this possible UAF by initializing the local variables after the skb_cow() call. Remove skb_reset_network_header() calls which were not needed.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 95b6d772bfe788331d9742d73eaa12e113b2adc4 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 7254aef4d1a7e18e887af9010e2f2dc34806789b (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < bf8b3f34c37c162357138e7c0942723b8b94fed1 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 76cd9398a0470257ab765bdf5f358a2af2e17934 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 50750d86a2e5266aba0c295483b3397843198b11 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < 6dff77899b9e9fe5d854abda3a98ad04e7229ef7 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < f3f204541f280a6ecb04503a0d6794d93990ca43 (git)
Affected: 4cb47a8644cc9eb8ec81190a50e79e6530d0297f , < b4bc94353050b1fa7b702bd4c6600710dd926cff (git)
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Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 5.10.259 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()\n\nSashiko found that iptunnel_pmtud_build_icmp() and\niptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr()\nbefore an skb_cow() call which can reallocate skb-\u003ehead.\n\nFix this possible UAF by initializing the local variables\nafter the skb_cow() call.\n\nRemove skb_reset_network_header() calls which were not needed."
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      "product_status:under_investigation": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63994.json",
      "version": "3"
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      "cve": "CVE-2026-63994",
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      "product_status:first_fixed": "2",
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      "product_status:recommended": "442",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63994",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63994.json",
      "version": "18"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.